The invention relates to a thin-type display device which comprises a transparent front wall which is provided with a display screen having a pattern of pixels, and a rear wall which extends parallel to said front wall, which display device includes at least an electron source and a duct structure, which cooperates with said electron source and extends substantially parallel to the front wall, and which comprises walls which are transverse to the rear wall, said rear wall and the walls forming the ducts of the duct structure.
Thin-type display devices are used for displaying monochromatic or colour images in vacuum tubes, plasma displays and plasma-addressed liquid-crystal display devices (PALC display devices).
A display device of the type mentioned in the opening paragraph is disclosed in United States Patent document U.S. Pat. No. 5,347,199 (PHN 13.197), in which a description is given of a display device which employs (multiple or ribbon-shaped) electron currents which initially extend substantially parallel to the plane of the front wall and, finally, are constrained to move in a direction transverse to the display screen so as to address the desired (luminescent) pixels of the display screen, either directly or by means of, for example, an addressing system. In the known display device, the ducts of the duct structure comprise so-called electron-propagation means which cooperate with the electron source to transport emitted electrons through vacuum. The electron currents, which are to be guided by the electron-propagation means, can be generated by means of an electron source or by means of an arrangement of a number of electron sources which are parallel to (an edge of) the front wall. The electron currents generated by the electron source(s) are guided by means of the propagation means (beam-guiding means) over at least a part of the height (or width) of the display device in the direction of one of the edges of the display screen. To make it possible for the electron current to leave the electron-propagation means in desired (successive) places, a beam-guiding means can be provided with a row of apertures with electrodes which can be energized either to withdraw or not to withdraw electron currents from the propagation means at the location of an aperture.
In plasma displays, electrons are generated in the ducts of the duct structure, which electrons address desired (luminescent) pixels of the display screen, either directly or by means of, for example, an addressing system. In plasma-addressed LCDs (PALC displays), a plasma having a relatively low energy level is generated in the ducts of the duct structure, which plasma converts the (plasma) duct of an (electrically neutral) insulator into a conductor. If a suitable voltage is applied to an electrode in a corresponding LCD element, the plasma provides for the conduction which is necessary to set the voltage across the LC element and hence control the transparency of the element.
A disadvantage of the known display device is that, during the manufacture of the duct structure, the interspace between the walls of the ducts, and hence the width of the ducts extending (transverse) to the rear wall is not constant. As a result, differences in (beam) intensity between adjacent ducts develop, which give rise to annoying streaks in the image displayed on the display screen by the pixels.